Dehairing skins



l atented July 18,-

UNITED STATES v PATENT OFFICE DEHAIRING SKINS Edward F. Christopher, Chicago, IlL assignor to Industrial Patents Corporation, Chicago, 111., a corporation of Delaware No Drawing. Application May 2 2, 1942, Serial No. 444,104

22 Claims. (01.8-94.16)

This invention relates to a method of treating hides and skins to prepare the hides and skins bath for-from about five days to seven days.

At theend of this soaking period the hides are removed and thoroughly washed. The hides are then subjected to a beaming operation in which the hides are scraped or beamed with a dull knife or blade to remove the hair and to squeeze out any wool or hair roots. This operation simultaneously removes foreign materials and dirt from the skin, but it is a costly operation because it is of necessity a hand operation. In this method for removing hair and wool, a considerable time is required and large spaces must be provided for the tanks in which the hides are treated with the lime liquor.

Numerous methods have been employed and have been proposed to hasten the dewooling and dehairing process or to provide a method of removing the hairor wool in a shorter period of time. Perhaps the most commonly used method of treating hides and skins for the removal of hair and wool consists of what may be classed as a two stage method including dewooling and dehairing the pelts. The skins or hides are dewooled by painting or treating the flesh side of the hide or skin with a depilatory consisting of a paste containing lime, sodium sulfide and water. The paste is generally prepared by mixing slaked lime with powdered sodium sulfide in a ratio of about 60 parts of lime to 40 parts of sulfide and the hides are agitated in the bath for a suflicient period of time to substantially remove the remaining fine hair and wool and the remaining hair or wool roots. This method-oi treating hides and skins permits the removal of the hair and wool in from two days to three days, however, the skins are afiected tqa much greater extent than in the older conventional method.

One of the principal objections to this method is that the skins become drawn. This condi-,' tion produces a loose grained leather and one side of the hide appears to draw or shrink to a greater extent than the other surface. The other principal objection to skins processed in this manner is that they do not possess the same degree of stretch or elasticity asskins processed in accordance with the older conventional manner.

Numerous compositions have been proposed, in-

cluding the use of various enzymes, various organicmaterials and various inorganic salts, for

cation, and many of the substances are so severe in their action that they injure the skin although a close control of the process is attempted.

The principal object of the present invention is to provide a method whereby the removal of hair and wool may be accomplished in a shorter periodof time than the older lime method but adding sufllcient water so that the paste may be skins which is more efficient in the removal of the painted on the skin or hide with a brush. The treated skins are -then allowed to remain in a cool place over night or for from about 16 hours to-24 hours to permit a penetration of the depilatory from the flesh side through the skin to the roots ofthe hair or wool. The skins are then subjected to mechanical action. as by rubbing,

jor portion of the wool and hair, however, some fine hair and some hair or wool roots remain. The skins treated with the depilatory and from which the wool has been pulled are generally known as dewooled skins. V

The dewooled skins are then dehaired by soaking the skins in a bath containing sodium sulfide, usually from about 1.3 per cent to 1.5 per cent for about 24 hours to '12 hours. The skins are then subjected to a reeling operation whereby which produces a type of skin which is substantially the same as the type of skin produced by this old method;

Another of the objects of this invention is to provide a method for treating dewooled hides and fine hair and hair or wool roots so that hand beamingof hides and skins is unnecessary.

Another object of this invention is to provide a method of treating dewooled hides and skins for the removal of residual hair arid hair or wool roots so as to yield a higher quality hide or skin for the subsequent preparation of leather.

The present invention contemplates the addition to an alkaline-sodium sulfide dehairing liquor of a small proportion of a water soluble inorganic and. peracetic anhydride. It will be obvious to those skilled in the art that other substances may be employed with equal efiectiveness. The term "water soluble" is used to designate a sufiicient solubility to form an aqueous solution of the required concentration for the purp ses of this invention. 1 a

It is well-known that the ordinary conventional alkaline solutions'or suspensions of sodium sulfide are relatively slow initheir dehairing action and various reagents have been added in an attempt to increase the rate of dehairing. However, these substances are generally injurious to the hides and skins. The reagents employed in the practice of the present invention are not injurious' to the hides and skins, and, in general, permit the use of smaller quantities of lime and sodium sulfide. In the practice of the present invention the reagent is added to the dehairing liquor, preferably during treatment of the hides with the liquor.

The liquor is first prepared by dissolving from about 0.1 per cent to 1.3 per cent, preferably from about 0.3 per cent to 0.5 per cent sodium sulfide in water. The dewooled hides or skins are then soaked in this solution, about 3 parts to 4 parts by weight of solution being employed for about each part by weight of hides or skins. The hides are reeled in this liquor or solution for about one hour. Lime is then added in the proportion of from about 1 per cent to 5 per cent, based upon the weight of the solution, and the hidesare again reeled for about one-half hour. The reagent is then added to and dissolved in the solution and the skins or hides again reeled for about one hour. The hides are then allowed to remain in the liquor for from 16 hours to 24 hours after which they are again reeled to. remove the swollen or pulped wool and hair. The hides are then separated from the liquor, thoroughly rinsed and are .ready for the subsequent hating and pickling operations.

'It is obvious to those skilled in theart, that the proportions which are set forth are not critical and may be varied. The reagents employed in the practice of the present invention are preferablyemployed in quantities between 0.1 per cent and 0.5 per cent. For certain special purposes it may be desirable to employ as much as 10 per cent of a particular reagent'or less than 0.1 per cent of a particular reagent. The smaller proportions are, of course, desirable from an economical consideration.

In specific illustrations, sheep skins were treated assasrs However, to remove the remaining b l d wool and hair, the skins were reeled for about one hour after which the liquor was drained from the skins and the skins thoroughly washed with water.

Skins treated in accordance with-the method described herein are free from all hair and hair roots and appear to remain unaffected in all other respects. The skins are not drawn and they possess about the same stretch or elasticity as skins processed by the straight lime method.

The precise nature of.the action of the particular reagents is not understood. However. the reagents greatly accelerate the dissolving or pulping of the hair and ,hair roots remaining after dewooling. At. the same time the action isv not so severe that it injures in any way the skins or hides. The improvementsin the dehaired skins may be due to the lower alkalinity of the dehairing bath or solution as compared to the conventional de-.

hairing solutions.

The term "dewooled skins" is employed herein and in the claims to designate hides and skins which have been subjected to the first stage in the method of removing hair and wool. This stage comprises treating the hide or skin with a depilatory and subjecting the treated hide or skin-to mechanical action whereby the major portion of the hair and wool is removed. The term dewooling istused to designate this first stage in the removal of hair and wool from hides and skins.

The term dehaired skins is used herein and in the claims to designate dewooled skins which have been subjected to a treatment which removes have been set forth as being merely illustrative bath.

I elm: 1 v

1. In a method of removing hair and wool from hides and skins, the step which comprises subjecting the hides and skins to the action of an aqueous alkaline medium containing lime, an alkali sulfide and a substance selected from the group consisting of water soluble inorganic and bypainting a lime-sodium sulfide-water paste on the flesh side of the skins and the skins held in a cool place over night. The following morning the skins were dewooled. About 80 pounds of the dewooled skins were soaked in about 280 pounds of sodium sulfide solution containing between 0.3 per cent and 0.35 percent sodium sulfide. The

skins were reeled in this solution'for about one hour and about, 1 per cent lime based upon the weight of liquor. Reeling was continued for'about one-half hour. About 0.1 per cent hydrogenperoxide, barium peroxide, calcium peroxide or sodium per-.

The following morning it was found that the greater proportion of hair and wool'remaining after-dewooling had been removed or dissolved.

the solution was added directly to the organic peroxides, peracids, peranhydrides, and such alkyl and acyl derivatives of hydrogen peroxide which tend to yield hydrogen peroxide in alkaline solutions.

2. In a method of removing hair and wool from hides and skins, the step which comprises subiecting the hides and skins to the action of an aqueous alkaline solution containing lime, an alkali sulfide and a small proportion of a substance selected from the group consisting of water soluble inorganic and organic peroxides. ,pcracids, peranhydrides, and such alkyl and acyl derivae tives of hydrogen peroxide which tend to yield hydrogen peroxide in alkaline solutions.

3. In a method of removing hair and wool from sulfide and a substance selected from the group consisting of water soluble inorganic and organic peroxides, peracids, peranhydrides, and such alkyl and acyl derivatives of hydrogen per-, oxide which tend to yield hydrogen peroxide in alkaline solutions.

4. In a method of removing hair and wool from hides and skim, the step which comprises subjecting dewooled hides and skins to the action of an aqueous medium containing lime, sodium sulfide and up to per cent of a substance selected from the group consisting of water soluble inorganic and organic peroxides, peracids, peranhydrides, and such alkyl and acyl derivatives of hydrogen peroxide which tend to yield hydrogen peroxide in alkaline solutions.

5. In a method of removing hair and wool from hides and skins,- the step which comprises soaking dewooled hides-and skins in an aqueous solution containing about 1 per cent to about 5 per cent lime, about 0.1 per cent to about 1.3 per cent sodium sulfide and from about 0.1 per cent to 0.5 per cent of a substance selected from the group consisting of water soluble inorganic and organic peroxides, peracids, peranhydrides, and such alkyl and acyl derivatives or hydrogen peroxide which tend to yield hydrogen peroxide in alkaline solutions.

6. In a method of removing hair and wool from hidesand skins, the step which comprises subper cent sodium sulfide and about 0.1 per cent to about 0.5 per cent hydrogen peroxide.

8. In a method of removing hair and wool from hides and skins, the step which comprises subjecting dewooled hides and skins to the action of an aqueous alkaline medium containing lime, an alkali sulfide and calcium peroxide.

9. In a method of removing hair and wool from hides and skins, the step which comprises -soaking dewooled hides and skins in an aqueous solution containing about 1 per cent to about 5 per cent lime, about 0.3 per cent to about 0.5 per cent sodium sulfide and about 0.1 per cent to about 0.5 per cent calcium peroxide.

10. In a method of removing hair and wool from hides and skins, the step which comprises subjecting dewooled hides and skins to the action of an aqueous alkaline medium containin lime, an alkali sulfide and sodium perborate.

11. In a method of removing hair and wool from hides and skins, the step which comprises soaking dewooled hides and skins in an aqueous solution containing about 1 per cent to about 5 per cent lime, about 0.3 per cent to about 0.5 per cent sodium sulfide and about 0.1 per cent to. about 0.5 per cent sodium perborate.

12. In a method of removing hair and wool from hides and skins, the-steps o1 soaking dewooled hides and skins in an aqueous solution of sodium sulfide, adding lime to the q e s solution and reeling the hides and skins in the resulting liquor, adding a small proportion of a substance selected from the group consisting of water soluble inorganic and organic peroxides, peracids, peranhydrides and such alkyl and acyl derivatives of hydrogen peroxide which tend to yield hydrogen peroxide in alkaline solutions, soaking the hides and skin in the resulting liquor for a sufiicient period of time to dissolve a substantial portion of the hair, reeling the hides and skins in the liquor and thereafter washing the hides and skins.

13. The method of accelerating the dehairing oi dewooled hides and skins by the use of alkaline dehairing liquors, which comprises adding to a lime-sulphide dehairing liquor an amount of a substance selected from the group consisting of water soluble inorganic and organic peroxides, peracids, peranhydrides, and such alkyl and acyl derivatives of hydrogen peroxide which tend to yield hydrogen peroxidein alkaline solutions.

14. The method of accelerating the dehairing of dewooled hides and skins by the use of alkaline dehairing liquors, which comprises adding to a lime-sulfide dehairing liquor a small proportion of hydrogen peroxide.

15. The method of accelerating the dehairing of dewooled hides and skins by me use of alkaline dehairing liquors, which comprises adding to a lime-sulphide dehairing liquor a small proportion of calcium peroxide.

16. The method of accelerating the dehairing of dewooled hides and skins by the use of alkaline dehairing liquors, which comprises adding to a lime-sulfide dehairing liquor of sodium perborate.

1'7. In a method of dehairing dewooled hides and skins by the action or alkaline medium containing lime and sodium sulfide, the improvement which comprises adding to the alkaline medium an amount of a substance selected from the group consisting of water soluble inorganic and organic peroxides, peracids, peranhydrides, and such alkyl and acyl derivatives at hydrogen peroxide which tend to yield hydrogen peroxide in alkaline solutions.

18. A dehairing liquor comprising lime, an alkali sulfide and a substance selected from the group consisting of water soluble inorganic and organic peroxides, peracids, peranhydrides, and such alkyl and acyl derivatives of hydrogen peroxide which tend to yield hydrogen peroxide in alkaline solutions.

19. A dehairing liquor comprising lime, sodium- 21. A dehairing liquor comprising lime, sodium .sulflde and calcium peroxide.

. 22. A dehairing liquor comprising lime, sodium sulfide and sodium perborate.

EDWARD I". CHRISTOPHER.

a small proportion 

